The correct option is A HNO3>H3PO4>H3AsO4>H3SbO4
Since all the elements are in the same oxidation state, electronegativity has to be considered. Electronegativity of the elements from N to Sb decreases generally. Thus N with high Electronegativity can donate the proton easily where as for Sb with least Electronegativity becomes difficult to donate proton. Thus (A) is the correct order.